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Abstract
The distribution of adhesive on strands is one of the key characteristics for the blending of oriented Strandboard (OSB) furnish. Optimizing the adhesive distribution on the strand surface will result in maximizing the panel properties while minimizing costs through lower resin usage. This paper describes a modified flexographic printing technique for applying adhesive to OSB-like strands and shows that in can be used, within a limited range, to produce droplet arrays on the surface of strands. The resin mass deposited onto the strand surface increases linearly with wire wound rod number. The variablitily of the mass applied was also found to increase with rod number and was significantly affected by resin temperature. The resin mass transferred using resin at room temperature was approximately four times that of the mass transferred when using resin at only 4[degrees]C. A model for the resin mass deposited onto the strands is also presented.
During the manufacture of OSB, resin is sprayed onto the strands in a rotary drum blender with an atomizer. The resin droplet size distribution produced by the atomizers can be controlled to a limited extent by manipulation of their operating parameters, but neither spinning disk atomizers nor spray nozzles permit precise control over the placement of droplets on the strand surface. Both atomizer types produce distributions with a broad range of droplet sizes and neither can produce resin droplets of uniform size. A question posed during the initial phase of this work was "What is better, many small droplets or a few large droplets?" In light of the various factors that come into play during pressing, it is not clear which of these choices is best. One of the long-term goals of this work is to determine the optimum resin droplet size to deposit on the strand surface that will maximize bond strength while minimizing the total resin mass applied and its associated cost. However, before that can be accomplished, a means of preparing fine dispersions of droplets on the strand surface is required. The flexographic printing technique is commonly used in the production of printed materials such as pictures in newspapers, brochures, and other printed items. Since the inks used in this process are often based on phenol-formaldehyde (PF) resins (Wells 1976), it...